JP3200654B2 - Projection exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for transferring a fine pattern such as a mask and a reticle onto a substrate such as a wafer.

2. Description of the Related Art A projection exposure apparatus for transferring a pattern such as an LSI on an original substrate onto a substrate to be exposed is required to have high resolution in response to the necessity of miniaturizing the pattern size of the LSI and the like. By the way, the resolution of these projection exposure apparatuses is
It has been considered that the numerical aperture when viewing the projection exposure optical system from one point on the substrate to be exposed is NA, and the wavelength of a light beam to be exposed is λ, and is generally proportional to λ / NA. However, in recent years, analysis and experiments have progressed, and the contrast of the pattern image on the original substrate projected and exposed on the substrate to be exposed, that is, the resolution, also depends on the state of the illumination light beam that irradiates the original substrate and enters the projection exposure optical system. It was found that sex changed greatly.

[0003] Japanese Patent Application No. 59-212269 discloses a high resolution by providing "a secondary light source irradiating a reticle with a special aperture that makes the exit surface intensity distribution that the peripheral intensity is larger than the central intensity". It is shown to be an image, and Japanese Patent Application Hei 3
-99822, Japanese Patent Application No. 3-148133, Japanese Patent Application No. 3
-157401, Japanese Patent Application No. 3-218100, Japanese Patent Application No. 3-218098, Japanese Patent Application No. 3-225335, Japanese Patent Application No. 3-235755, Japanese Patent Application No. 3-254306, Japanese Patent Application No. 3-290442. A number of methods and apparatuses for irradiating light incident on a reticle at an angle corresponding to the numerical aperture of a projection exposure optical system or at an angle smaller than that are proposed.

However, in these applications,
In any case, it is implicit that the intensity distribution at the time of emission of the secondary light source that irradiates the reticle is ideal, and that the light intensity is uniform in the range of each shape of the secondary light source specified in each of the above-mentioned applications. Is assumed within. Therefore, none of the above-mentioned applications mentions any non-uniformity of the intensity distribution or the emission azimuth distribution in the emission shape of the secondary light source that irradiates the reticle, and of course does not mention any measures for achieving the uniformity. Not.

FIG. 13 shows a basic structure of an optical system of a conventional projection exposure apparatus. Light emitted from a primary light source 67 such as an ultra-high pressure mercury lamp or an excimer laser passes through a first illumination optical system 68 and is guided to a uniforming optical system 69. Uniform optical system 69
In most cases, an optical integrator called a fly-eye lens formed by integrating a set of rod-shaped lenses having a small cross-sectional dimension or an assembly of the rod-shaped lenses is used.

[0006] the light emitted rod-shaped fly-eye lens each so as to irradiate the original drawing board 71 by via the second illumination optical system 70, the light incident on the optical integrator consisting of the fly's eye lens by the superposition effect Even if there is a variation or distribution in the intensity or direction, the uniformity of the illumination light in the exposure area on the original drawing substrate 71 is made as good as possible. The pattern to be exposed on the original substrate 71 illuminated by the second illumination optical system 70 is transferred onto the substrate to be exposed 73 through the projection exposure optical system 72.

FIG. 14 is a sectional view more specifically showing an example of an illumination system of a projection exposure apparatus using an ultra-high pressure mercury lamp as a light source. Ultra-high pressure mercury lamp 74 with elliptical mirror 7
5, the light emitted from the ultra-high pressure mercury lamp 74 in all directions is once collected at the second focal point of the elliptical mirror 75 via the plane mirror 80. Thereafter, the light beam is converted into light substantially parallel to the optical axis by the input lens 76, and the light is extracted through a filter 77 into a single light color required for exposure, and is input into an optical integrator 78. Since the ultra-high pressure mercury lamp 74 cannot extract light in the axial direction of the lamp, in the optical system shown in FIG. 14, light entering the input lens 76 is weak at the center and strong at the periphery.

In a conventional general projection exposure apparatus, light emitted from the entire area of the light emitted from the optical integrator 78 or light emitted from the center is used. Therefore, FIG.
As shown in FIG. 7, a cone lens 79 for bringing the light of the peripheral portion to the central portion is inserted, and the optical integrator 78 is provided.
The strength of the central part with respect to the
If you can not put it higher. Japanese Patent Application No. 59-2112
In an apparatus disclosed in Japanese Patent Application No. 69-167 and Japanese Patent Application No. 3-167491, which exposes only the light from the peripheral portion of the optical integrator 78 or the light from the peripheral portion more strongly than the central portion, the cone lens 79 is not required. Light can be collected more effectively.

The elliptical mirror 75 and the plane mirror 8 shown in FIG.
The optical system including the input lens 76, the input lens 76, the filter 77, and the cone lens 79 corresponds to the first illumination optical system 68 shown in FIG.
Corresponding to homogenizing optical system 69 shown in the aperture stop 81 Togazu 13 is installed on the exit side of the optical integrator 78. The reticle 85 corresponds to the original substrate 71 shown in FIG. 13, the reduction projection lens 86 corresponds to the projection exposure optical system 72 in FIG. 13, and the wafer 87 corresponds to the substrate 73 to be exposed in FIG. An aperture stop 88 provided in the reduction projection lens 86 is a stop for determining the numerical aperture NA of the projection exposure optical system. In addition, 89 of FIG. 14 is a lamp house.

[0010] instead of the light source an ultra-high pressure mercury lamp 74, when using the excimer laser is not necessary to use a condensing optical system such as ellipsoidal mirror 75, for erasing the laser speckle, for example Japanese Patent Application No. Sho It is necessary to install an optical system devised as disclosed in Japanese Patent Application No. 58-100689 or Japanese Patent Application No. 63-22131 in the first illumination optical system 68.
Uniformization optical system 69 and later, is basically similar to the case of the light source an ultra-high pressure mercury lamp 7 4. In the optical system of the projection exposure apparatus as described above, when viewed from the original drawing substrate, the illuminating light looks as if it comes from the exit side of the uniform optical system as the light source.
Is called a secondary light source.

When the light in the entire exposure area is used, the cross-section perpendicular to the axis of each element lens constituting the optical integrator 78 should be as similar as possible to the shape of the pattern area (exposure area) of the reticle 85. Good. This is because the exposure area is the optical integrator 7
8 is illuminated in the form of a cross-sectional shape of each element lens, and if an element lens having a shape similar to the shape of the pattern area is used, almost all of the light that has exited the optical integrator 78 will be emitted. This is because the pattern area is irradiated. Conversely, if a reticle 85 having a rectangular pattern area is irradiated by an optical integrator 78 formed by assembling element lenses having a circular cross section, light of a portion obtained by subtracting a quadrangle from a circle will be a pattern on the original substrate. Since the light is irradiated around the area and is not effectively used for exposing the pattern area, the light amount is also lost.

Therefore, a reticle 8 having a rectangular or square pattern area like an LSI chip
When 5 is used, the sectional shape of each element lens constituting the optical integrator 78 at right angles to the axis is often rectangular or square. For example, as shown in FIG.
The element lenses 90 each having a rectangular or square cross-sectional shape are regularly arranged and used closely in two orthogonal directions. With such a configuration, the light beam incident on the optical integrator 78 can be directed to the pattern area on the reticle 85 without waste.

By the way, an element lens 90 shown in FIG.
When the light passing through the central portion is taken out by the circular opening 91 and used, the intensity distribution in the exposure area (pattern area) of the reticle 85 is relatively uniform. Thus, even if the size of the circular opening 91 changes slightly, the non-uniformity does not increase much.

Here, the numerical aperture when viewing the projection exposure optical system 72 (reduction projection lens 86) from the original drawing substrate 71 (reticle 85) shown in FIG. 13 is NAp, and the original drawing substrate 71 passes through the second illumination optical system 70. When the numerical aperture when viewing the secondary light source on the emission side of the uniformizing optical system 69 is NAi, the size of the aperture on the emission side of the optical integrator 78 is generally standardized and expressed by a coherency factor σ = NAi / NAp. .

When the projection exposure optical system 72 is viewed from the substrate 73 to be exposed, an i-line reduction projection exposure apparatus having a numerical aperture NA of 0.35 is used, and σ = 0.
In the range of from 25 to 0.65, results of examining the non-uniformity of the light intensity distribution in the exposure region while changing various sizes of the circular opening 91 generally ± 2% following data was obtained. In FIG. 15, each element lens 90 has a vertical cross-sectional dimension of 4.5 mm and a horizontal width of 4 mm, and a marginal opening (diameter 24 mm of the circular opening 91) corresponds to σ = 0.65.

[0016]

Since the conventional projection exposure apparatus is configured as described above, a conventional projection exposure apparatus is provided on the exit side of the optical integrator 78 shown in FIG.
No. 211269, Japanese Patent Application No. 3-148133, Japanese Patent Application No. 3
When a circular or partial circular opening is provided as shown in JP-A-235575, Japanese Patent Application No. 3-254306, and Japanese Patent Application No. 3-290442, the uniformity of the intensity distribution in the exposure area is significantly deteriorated. I do. For example, on the emission side of the optical integrator 78 shown in FIG.
When a circular ring-shaped opening with a changed center light-shielding ratio with respect to the opening radius of the circular opening 91 is provided under the condition (1), as shown in FIG. It can be seen that the uniformity of the distribution is remarkably deteriorated, which leads to a large decrease in the exposure margin in practical use.

For example, when manufacturing an actual LSI,
When a fine pattern is transferred, a new fine pattern is transferred onto the substrate to be exposed on which another fine pattern has already been formed, so that a new fine pattern is transferred. Even when the exposure amount at the time is the same as that of the underlying fine pattern, the pattern size and shape tend to vary. Therefore, as described above, when the exposure amount itself from the secondary light source varies as described above, the size and shape of the pattern to be transferred greatly vary due to the influence of the already formed lower layer fine pattern. In addition, since each of these factors together causes variations in pattern dimensions and shapes, it is not possible to determine whether the causes of pattern variations are the influence of the base or the optical system of the projection exposure apparatus. As a result, a high-performance LSI cannot be obtained.

Further, as shown in Japanese Patent Application Nos. 59-212269 and 3-148133, contrivance is made to collect incident light on a circular or partial circular portion around the optical integrator 78. Is performed on the incident side of the optical integrator 78, the deterioration of the uniformity of the light intensity distribution in the exposure region cannot be improved only by increasing the utilization of the light beam.

The cause of the uneven exposure intensity in the above-described exposure area when the circular or partial circular light source is used as the secondary light source will be described below. First, the state of light passing through the element lens constituting the optical integrator 78 will be described. FIG. 17 shows a cross section including the axis of the rod-shaped element lens constituting the optical integrator 78 of FIG. FIG.

The light incident on the optical integrator 78 is determined by the fact that the original light source is not a point light source but has a size, that the first illumination optical system 68 in FIG. 13 has an aberration, and that the light source has coherence. The divergence angle α is provided for various reasons, such as a case where the divergence may be intentionally slightly increased for adjustment.

When tracking the way of light entering the element lens 90a, the light incident at the spread angle α
17a is refracted by the entrance surface 93 and the exit surface 94 of FIG.
As shown in FIG. 17A, they intersect within the element lens 90a, intersect at the point where the element lens 90b exits as shown in FIG. 17B, or as shown in FIG. Intersect near. That is, the element lens 90a shown in FIG. 17A is used when the focal point of the light entering from the incident surface 93 is within the element lens 90a.
b indicates that the focal point of light entering from the incident surface 93 is the element lens 90b.
18A, the element lens 90c in FIG. 18A and the element lens 90d in FIG. 18B have a case where the focal point of the light entering from the entrance surface 93 is approximately on the exit surface 94. Each is shown.

These element lenses 90a, 90b, 90
If the light entering c is light from an infinitesimal point or perfectly parallel light, all the light is concentrated and focused at one point, but the light entering those elemental lenses has a divergence angle. Since it has α, it cannot be completely focused.

FIGS. 17 (a), (b), and FIG.
In (a), light emitted from an arbitrary point on the incident surface 93 does not hit the side walls of the element lenses 90a, 90b, and 90c, but does not irradiate the entire area of the exit surface 94. On the other hand, after the incident light is refracted by the entrance surface 93, the exit surface 9
4 before reaching a part thereof.
If it hits the side wall of b, 90c, light that enters at any one point on the incident side at the spread angle α can irradiate the entire area of the exit surface 94. In the case of FIG. 18A, the light that has entered the element lens 90d from an arbitrary point on the incident side and spreads out from the arbitrary point on the exit surface 94 as shown in FIG.
If the optical constants and dimensions of the element lens are selected so as to cover the lens, almost no light is applied to the side wall of the element lens 90d.
The entire area of the exit surface 94 can be irradiated.

As described above, the uniformity of the light illuminating the original substrate is improved when the light coming from all the points on the entrance side of the element lens is superimposed on the exit side of the element lens. Needless to say. Here, consider a case where an aperture stop is placed on the exit side of the element lens. For example, if an aperture stop 95 is provided on the emission side in FIG. 18B as shown in FIG. 19A, light that can pass through the aperture stop 95 from point A in FIG. As shown by the oblique lines in FIG. 19A, the light becomes a part of the light emitted from the point A, and it becomes impossible to irradiate the entire exposure area only with the light emitted from the point A and passing through the aperture stop 95. Of these, only those having an angle within a predetermined range contribute to the illumination of the original drawing substrate.

Light incident on arbitrary points B, C,... Other than the point A on the incident side of the element lens 92 is similarly transmitted through the aperture stop 95.
And the light incident from the point A illuminates only the place other than the place where the original substrate can be illuminated.
The example shown in FIG. 19A is a case where light entering the element lens 90d from an arbitrary point on the incident side in FIG. 18B irradiates the entire area of the exit surface 94.
As shown in (a), (b), and (c), when light entering the element lenses 90a, 90b, and 90c from any one point of the incident angle does not irradiate the entire area of the exit surface 94, an aperture stop is used. Depending on the position of the incident point at the position 95, most or all of the light that has entered the element lenses 90a, 90b, and 90c from that incident point may be cut off.

When the exposure area of the original substrate is illuminated in a state as shown in FIG. 19A, all places in the exposure area are illuminated by light coming from a position on the incident side of the element lens 92. However, points A, B, and
Since the light is not equally irradiated from C ..., the uniformity of illumination in the exposure area is deteriorated. Then, FIG.
As shown in (b) and (c), when light enters the element lenses 90a, 90b, and 90c from an arbitrary point on the incident side and does not irradiate the entire area of the exit surface 94, the uniformity of illumination is further deteriorated. I do.

Here, the case where the aperture stop is provided for the emitted light for each element lens has been described above, but the element lenses are combined as an optical integrator 78 as shown in FIG. In the state, FIG.
In as indicated by oblique lines, the case of providing the circular ring-shaped aperture stop on its exit side, one single element lens 90 is positioned in the opening area, the shape is different. Therefore, in addition to the poor uniformity of the light coming from each of the element lenses 90, the light having a poor uniformity from many of the element lenses 90 is superimposed on the intensity distribution and the angle distribution of the light rays completely differently. The uniformity of illumination for irradiating the exposure area is deteriorated.

When the circular aperture stop shown in FIG. 15 is used, the element lens 9 at the center of the circular aperture 91 is used.
0 indicates that the light amount from the element lens 90 that is used uniformly over the entire area is larger than the light amount from the element lens 90 whose part or most of the light is blocked by the circular aperture stop. Irradiates the exposure area, so that its uniformity does not deteriorate.

[0029] The present invention has been made to solve the above problems, in a projection exposure apparatus using a circular ring or circular ring-shaped secondary light source, improve the illumination uniformity of the original, the substrate exposure area The purpose is to let them.

[0030]

A projection exposure apparatus according to the present invention uses a set of element lenses or an integrated element lens group as an optical integrator, and uses the light emitted from the optical integrator as a secondary light source to perform projection exposure. through an optical system, a projection exposure apparatus for transferring a pattern of originals on a substrate on a substrate to be exposed, optical
Light incident on the integrator is circular or partial circular
The collected light, the center of which is approximately
On the circumference of one circle whose radius is the radius of the ring , or on a circle
Der those as provided with an optical integrator arranged so as to line up on top of the arc of the radius of the wheel radius
You.

[0031] In addition, the projection exposure apparatus of the present invention, the elements Les
Lens assembly or integrated element lens group
Used as an optical integrator,
Using the light emitted from the grater as a secondary light source, a projection exposure optical system
To transfer the pattern on the original substrate onto the substrate to be exposed.
In a projection exposure apparatus, the center of the element lens is
So that they line up on the circumference of a circle or on an arc
The optical integrator has an optical integrator, and on the exit side of the optical integrator, a circular or partial annular aperture stop, or a stop in which the light transmittance of the peripheral portion is larger than the light transmittance of the central portion is provided. The approximate position of the circumference or arc of the circle where the center of the lens is located is within the range of the aperture of the aperture stop of the ring or partial ring, or the light transmittance of the peripheral part is larger than the light transmittance of the center part
The light transmittance at the periphery of the aperture stop is in a large range .

[0032]

The original substrate illumination can be taken out from the entire exit surface of each of the element lenses of the optical integrator or from a considerably large area, and light rays close to the optical axis of each of the element lenses can be used. An arbitrary point in the exposure area on the original drawing substrate is illuminated by many element lenses under almost uniform conditions.

[0033]

(Embodiment 1) FIG. 1 is a sectional view showing an arrangement of element lenses of an optical integrator in a direction perpendicular to an axis according to an embodiment of the present invention. Reference numeral 1 denotes an element lens having a square cross section perpendicular to the axis, reference numeral 2 denotes a circle on which the element lens 1 is arranged, and reference numeral 3 denotes an intersection of the circle 2 and a straight line forming 45 ° with the X axis and the Y axis. Here, when the projection exposure using a circular ring-shaped secondary light source, the radius of the circular ring that requires r, when the width of the circular ring and b, and the element lens 1 on a circle 2 of radius r The conditions for arranging closely are described below.

The x direction on the substrate where the pattern is exposed,
In order to make the irradiation conditions in the y direction the same and make the resolution the same, it is necessary to arrange the element lenses symmetrically in the x and y directions. The conditions for this are X-axis, Y-axis and 4
This means that the element lenses are arranged symmetrically with respect to a straight line forming 5 °.

As shown in FIG. 1, an element lens is first placed on an intersection 3 between a straight line forming 45 ° with the X axis and the Y axis and a circle having a radius r.
When the center of the lens 1 is placed, the element lenses 1 are arranged closely so that the center passes on the circle 2, and the perpendiculars drawn from the center of the element lens 3, that is, the intersection 3 to the X axis and the Y axis, respectively. Is set to n of the length a of one side of the element lens 1.
/ 2 times (n is a positive number). Therefore, the length h of the perpendicular is expressed by the following equation.

H = r / √2 = na / 2 (n = 1, 2,...) (1)

Therefore, the radius r of the circle 2 and one of the element lenses 1
The length a of the side must satisfy the relationship of the following equation.

R = na / √2 (n = 1, 2,...) (2)

In order to make the length a of one side of the element lens 1 equal to the required width b of the circular ring, a = b.
The following equation holds:

R = nb / √2 (n = 1, 2,...) (3)

Therefore, in order to make the irradiation conditions in the x direction and the y direction on the substrate on which the pattern is exposed the same and to make the resolution the same, the element lens is moved in the x direction and the y direction by 45 degrees.
The condition for symmetrical arrangement with respect to the straight line of ° is that the following equation holds.

R / b = n / √2 (n = 1, 2,...) (4)

That is, if the radius of the circle 2 on which the element lenses 1 are arranged is n / √2 times the width b of the ring through which light is to be transmitted, the cross-section perpendicular to the axis is a square having a side length a. A certain element lens can be arranged without any gap on a circle 2 having a radius r and a shape similar to a circle having a radius r and a width b.

As described above, since the element lenses 1 each having a square cross section perpendicular to the axis are arranged so that their centers are located on the circle 2, all the light that enters each element lens 1 and reaches the exit surface is emitted. The entire exit surface of each element lens 1 serves as a secondary light source, and the original substrate is superimposed by light emitted from the area in front of the exit surface of each element lens 1 under the condition that the exit area and the exit angle distribution are equal. Irradiated. Therefore, the illumination of the original substrate becomes uniform light with little variation in intensity and irradiation angle distribution depending on the location in the exposure region. The contour shape of the secondary light source in which the element lenses 1 are gathered is almost a circle.
Is Jo, also in regard to the transcription of a fine pattern can be central radius r, in the case of using a circular ring-shaped secondary light source of the width b to obtain substantially the same projection exposure characteristics.

(Embodiment 2) FIG. 2 is a sectional view showing an arrangement of element lenses of an optical integrator in a direction perpendicular to an axis, showing a second embodiment of the present invention. Reference numeral 4 denotes an element lens having a square cross section perpendicular to the axis, similarly to the element lens 1 of FIG. 1, and is arranged such that the center thereof is located on a circle 5. The arrangement of the element lens 4 is different from that of the element lens 1 of FIG. 1, and is arranged on a straight line that forms 45 ° with the X axis and the Y axis.
Is not placed, and the corners of the two element lenses 4 are arranged on a straight line that forms 45 ° with the X axis and the Y axis. Radius r in this case
The conditions for closely arranging the element lenses 4 having the length a on one side on the circle 5 are described below.

From the center 6 of the square element lens 4 whose angle is on a straight line forming 45 ° with the X axis and Y axis, the length hy of the perpendicular line lowered from the center 6 to the X axis is the length of one side of the element lens 4 Since a must be n times a (n is a positive integer) times a, the following equation holds.

Hy = na / 2 (n = 1, 2,...) (5)

On the other hand, since the distance connecting the center 7 of the optical integrator and the center of the element lens 4 is r, hx in FIG. 2, which is a vertical line lowered from the element lens 4 to the Y axis, can be expressed by the following equation.

Hx = hy + a (6)

The following equation is established between the distance r connecting the center 7 of the optical integrator and the center of the element lens 4 and hx, hy.

R = (hx ² + hy ² ) ^1/2 (7)

Here, the following equations are derived by substituting equations (5) and (6) into equation (7) .

[0053] r = ((hy + a) 2 + hy 2) 1/2 = a · (n 2/2 + n + 1) 1/2 ··· (8)

If the length a of one side of the element lens 4 is made equal to the required width b of the ring, the following equation is established by replacing a in equation (8) with b.

[0055] ^{r = b · (n 2/} 2 + n + 1) 1/2 ··· (9)

If the relationship between the radius r and the width b is determined so as to satisfy the equation (9), the element lenses can be arranged in a shape similar to a circle having a radius r and a width b. Example 2
In the case of the above, since the element lenses 4 each having a square cross section perpendicular to the axis are arranged so that the center thereof is located on the circle 5, all the light that enters each element lens 4 and reaches the exit surface is emitted without being interrupted. In addition, the entire exit surface of each element lens 4 serves as a secondary light source. In addition, light is emitted from the entire exit surface of each element lens 4 under the condition that the exit area and the exit angle distribution are equal, and these lights are superimposed. Then, the original substrate is irradiated. Accordingly, the illumination of the original drawing substrate is uniform light in which the intensity, the illumination angle, and the illumination distribution vary little depending on the location in the exposure area.

[0057] contour of secondary light source element lens 4 are assembled is substantially circular ring-shaped, with regard transfer of a fine pattern, the center radius r on the exit side of the conventional optical integrator, circular ring-shaped having a width b The same projection exposure characteristics as when an aperture stop is provided can be obtained. By the way, the sequence of Figure 2 appears to have no therewith emphatic 1, array element lens 4 of Figure 2 is biased to place the X-axis and Y-axis direction in the presence of the element lens 4, X-axis and Y 45 from axis
° Light from an inclined direction is slightly weaker than light from other directions. Therefore, when comparing the arrangement of FIG. 1 with the arrangement of FIG. 2, the arrangement of FIG. 1 is closer to a circular light source, whereas the arrangement of FIG. 2 is divided on the X axis and the Y axis. Close to a circular light source.

When the pattern to be transferred is only in the x and y directions, as shown in Japanese Patent Application No. 3-254306, the partial circular light source divided by the X axis and the Y axis is Is a high resolution, while the partial circular light source has X
The resolution of the pattern in the direction of 45 ° with respect to the Y axis and the Y axis decreases. In other words, when the pattern to be transferred is omnidirectional, the arrangement shown in FIG. 1 is preferable, and the pattern to be transferred is
In the case of only the axial direction, the arrangement of FIG. 2 is preferable.

(Embodiment 3) FIG. 3 is a sectional view showing the arrangement of element lenses of an optical integrator in a direction perpendicular to an axis, showing a third embodiment of the present invention. 8 is a rectangular element lens whose cross section perpendicular to the axis is different from the case of FIGS.
Reference numeral 9 denotes a circle in which the center of the section perpendicular to the axis of the element lens 8 is arranged. When the exposure area is rectangular, it is advantageous from the viewpoint of light collection efficiency to make the element lenses rectangular and arrange them closely so that the light emitted from each element lens of the optical integrator is condensed into a rectangle. Becomes In this case, the conditions for closely arranging the element lenses 8 having the long side length l1 and the short side length l2 on the circle 9 having the radius r are described below.

When the n2 rectangles are arranged side by side on the circle 9 with the left side and the right side, which are the long sides, adjacent to each other symmetrically with respect to the Y axis (the hatched element lens 8 in FIG. 3).
The distance lx in the x direction between the centers of the element lenses 8 at both ends of the n2 rectangular element lenses 8 can be expressed by the following equation.

Lx = l2 (n2-1) (10)

If the angle between the centers of the rectangles at both ends of the n2 rectangles and the intersection of the X-axis and the Y-axis with respect to the Y-axis is θ, the following equation is established.

Sin θ = lx / 2r = l2 (n2-1) / 2r (11)

On the other hand, among the n2 element lenses 8, n1 element lenses are provided between the element lenses 8 at both ends.
The upper and lower sides, which are the short sides, are adjacent to each other in a circle 9 symmetrically with respect to the X axis.
When vertically arranged while placing the center on the top (element lens 8 indicated by a horizontal line in FIG. 3), between the element lenses 8 at both ends of n2 rectangles (element lens 8 indicated by a diagonal line in FIG. 3) The distance between the centers in the y direction can be expressed by the following equation.

Ly = l1 (n1 + 1) (12)

If the angle between the center of the element lenses 8 at both ends of the n2 element lenses 8 indicated by oblique lines and the X axis centering on the intersection of the X axis and the Y axis is φ, the following equation is established. I do.

Sin φ = l1 (n1 + 1) / 2r (13)

On the other hand, as is apparent from FIG. 3, φ = π / 2
Since −θ, sinφ = cos θ, and the left side of Expression (13) becomes cos θ, and the following equation holds.

Tan θ = l2 (n2-1) / l1 (n1 + 1) (14)

Since sin ² θ + cos ² θ = 1, the following equation holds.

[0071] ^{l1 2 (n1 + 1) 2} + l2 2 (n2 + 1) 2 = r 2 ··· (15)

If l 1 and l 2 are set to values close to the required width b of the circular ring, illumination under substantially the same conditions as in the case where the circular light source is used as the secondary light source can be used. And FIG.
As shown in (1), the uniformity of illumination in a rectangular exposure area can be improved as compared with a conventional optical integrator in which a circular aperture stop is arranged on the exit side of the optical integrator.

In the third embodiment, as in the first and second embodiments, the element lenses 8 are arranged so that the centers thereof are located on the circles 9. The reaching light is not partially blocked by the aperture stop, etc.
All are emitted, and the entire exit surface of each element lens 8 becomes a secondary light source. Then, the light emitted from the exit surface of each element lens 8 is illuminated in a superimposed manner under the condition that the exit area and the exit angle distribution are uniform, so that the original substrate irradiated with the light is irradiated. Both the light intensity and the irradiation angle distribution become uniform light with little variation depending on the location in the exposure area where the pattern is transferred.

[0074] FIG. 3, the contour shape of the secondary light source element lens 8 are assembled are substantially circular, with regard transfer of a fine pattern, a conventional, central radius r, the diaphragm circular ring-shaped opening having a width b Can be obtained on the exit side of the optical integrator to provide substantially the same projection exposure characteristics as when a secondary light source is used.

(Embodiment 4) In the above embodiment, the element lenses to be arranged have the same cross section perpendicular to the axis.
A square element lens and a rectangular element lens may be arranged in combination. When the secondary light source of the projection exposure apparatus is circular illumination, the width b of the circular ring also affects the resolution. Therefore, the optical integrator of the third embodiment in which the rectangular element lens 8 shown in FIG. If the width in the radial direction is different between the X axis and the Y axis as described above, the resolution of the pattern to be transferred is different between the x direction and the y direction. That is, in this case, when a vertically arranged rectangular pattern is transferred, the resolution in the long side direction and the resolution in the short side direction of the rectangular pattern are different.

FIG. 4 is a sectional view showing the arrangement of the element lenses of the optical integrator according to this embodiment in a direction perpendicular to the axis. FIG. 4 shows a dimension corresponding to the width b of the ring as x
The element lens 10 has the same length as the long side of the element lens 8 having a square cross section perpendicular to the axis and a rectangular side, and the other elements have the same configuration. It is the same as FIG. When the exposure area is rectangular, the light rays entering the left and right ends of the square element lens 10 are as follows.
Since the light illuminates the outside of the exposure area, the light use efficiency is reduced.
However, it can be moved in a direction to obtain substantially the same resolution in the x direction and the y direction.

Also in the case of the fourth embodiment, the element lenses 8, 1
Since each center of 0 is arranged on the circle 9, all the light that enters each element lens 8 and 10 and reaches the exit surface is emitted, and the entire exit surface of each element lens 8 and 10 becomes a secondary light source. Each of the element lenses 9 and 10 emits light having a uniform emission area and uniform emission angle distribution, and these overlap and illuminate the exposure area. The contour shape of the secondary light source in which the element lenses 8 and 10 are gathered is almost circular, and the secondary light source in which a circular aperture stop is arranged on the exit side of a conventional optical integrator is also used for transferring a fine pattern. Thus, substantially the same projection exposure characteristics can be obtained.

(Embodiment 5) In the above embodiment, the element lenses are arranged in one line on a circle. However, element lenses may be further arranged inside or outside the element lenses arranged on the circle. FIG. 5 is a cross-sectional view showing an example of an optical integrator of a projection exposure apparatus, showing an example in which element lenses are further disposed inside and outside the element lenses arranged in a ring shape shown in FIGS. . If light is incident on the entire area of the disposed element lenses 15 to 18, the illumination uniformity is further improved by the increase in the number of element lenses.

The light beam having a ring-shaped area may be incident only on the vicinity of the element lenses 15 to 18 arranged on the circles 11 to 14 of this optical integrator. In the first to fourth embodiments, the element lenses 1, 4, 8, and
Because the shape of the contour of the element lens group consisting of 10 is complicated,
It is difficult to condense all the light incident on the optical integrator composed of the element lens groups only at the portion where the element lens groups exist, and the light collection efficiency is reduced.

However, if the light is incident only on the vicinity of the element lenses 15 to 18 arranged on the circles 11 to 14, it is possible to use all the incident light without waste, and it is possible to increase the light use efficiency. . FIG. 5 shows circles 11-1.
Although the element lenses are further arranged on both the outside and the inside of the element lenses 15 to 18 arranged on 4, the element lenses may be arranged only on the outside or the inside, and further, the arrangement of the element lenses on the outside and the inside. May be increased.

Although FIGS. 5A and 5B are similar, the locations where the element lens 15 and the element lens 16 exist are different, and the element lens 16 is deviated in the X-axis and Y-axis directions. , Light from a direction inclined by 45 ° from the Y axis is slightly weaker than light from other directions. Therefore, FIG. 5 (a) is more similar to a normal circular light source than FIG. 5 (b), whereas FIG. 5 (b) is divided into four parts by the X axis and the Y axis. The resolution is slightly different, depending on the direction of the pattern to be transferred. FIG.
In the case of the arrangement shown in FIG. 5B, all the element lenses 16 can have the same cross-sectional shape perpendicular to the axis, and a part of the inner element lens 15 is partially angled as shown in FIG. There is also an advantage that it is not necessary.

(Embodiment 6) In the embodiment described above, the case where the entire cross section of the element lens of the optical integrator is used for exposure has been described. However, as shown in the prior art, for example, Japanese Patent Application No. 59-212269. An aperture stop in the shape of a circular or partial ring, or an aperture stop made so that the light transmittance of the peripheral portion is larger than the light transmittance of the central portion, is combined with the optical integrators of Examples 1 to 5. May be combined.

FIGS. 6 and 7 show an annular aperture stop having a width substantially equal to the length of the side of the element lens according to the first to fifth embodiments of the present invention shown in FIGS. 1 to 5 on the exit side of the optical integrator. It is sectional drawing which shows the state which arrange | positioned. Figures 6 and 7
In 19, 21, 23, 25, 27, 29, 3
Reference numerals 1 and 33 denote circles indicating the outside of the opening area of the annular aperture stop,
Reference numerals 20, 22, 24, 26, 28, 30, 32, and 34 denote circles indicating the inside of the opening area of the annular aperture stop.
9, 21, 23, 25, 27, 29, 31, 33 and circle 2
The area sandwiched between 0, 22, 24, 26, 28, 30, 32, and 34 indicates the aperture area of the annular aperture stop. By doing so, the light illuminating the original drawing substrate has a more accurate circular shape, and almost all areas of the element lenses in the circular opening are used, and illumination uniformity is good.

Although FIGS. 6 (a) and 6 (b) are similar, the same can be said for FIGS. 5 (a) and 5 (b).

(Embodiment 7) FIG. 8 shows a state in which a ring-shaped aperture stop having a width larger than the side length of the element lens is arranged on the exit side of the optical integrator shown in FIG. FIG. In FIG. 8, 3
5, 37, 39 and 41 are circles indicating the outside of the opening area of the annular aperture stop, and 36, 38, 40 and 42 are circles indicating the inside of the opening area of the annular aperture stop and circles 35, 37 and 3 are shown.
The area sandwiched between 9, 41 and the circles 36, 38, 40, and 42 indicates the aperture area of the annular aperture stop. With this configuration, the light irradiating the original drawing substrate surely becomes a circular light source, and as shown in FIG. 8, each element lens coming to the center of the opening of the circular aperture stop covers the entire area. Since it is used, illumination uniformity is also improved.

When the opening width of the annular aperture stop is about twice the length of the side of the element lens, the circle where the center of the element lens is located is positioned at the center of the opening of the annular aperture stop. Instead of being placed between the element lens group on the circle and the element lens group inside or outside the element lens group,
The center of the opening of the circular aperture stop may be positioned. With this configuration, the uniformity of illumination is improved because the element lens group that comes into the opening of the annular aperture stop uses almost the entire area of the cross section as a secondary light source.

Incidentally, also in this embodiment, FIG.
5A and FIG. 8B are similar, but FIG. 5A and FIG.
This is the same as the case (b).

Embodiment 8 FIGS. 9 and 10 show a ring-shaped aperture stop having a width smaller than the side length of the element lens of the optical integrator shown in Embodiments 1 to 5 of the present invention. It is sectional drawing which shows the state arrange | positioned at the injection side. 9 and 10, 4
3,45,47,49,51,53,55,57 are circles 44,46,4 indicating the outside of the opening area of the annular aperture stop.
Reference numerals 8, 50, 52, 54, 56, and 58 denote circles indicating the inside of the opening area of the annular aperture stop.
49, 51, 53, 55, 57 and circles 44, 46, 48,
The area sandwiched by 50, 52, 54, 56, and 58 indicates the aperture area of the annular aperture stop.

In this case, the light emitted from the element lens is restricted by the annular aperture stop. However, as shown in FIG. 9, each element lens is located at the center of the aperture stop. The size of the opening differs only at most about the ratio of the length of the side of the element lens to the diagonal length of the element lens. Therefore, light from each element lens is used almost equally. As a result, as shown in FIG. 19B, the conventional annular aperture stop arbitrarily opens a part of the element lens, and the opening area is also small. Compared to the case of an optical integrator that uses element lenses that are completely different in location,
The illumination uniformity is significantly improved.

FIGS. 17A and 17B and FIG.
In the case of an element lens having an optical system in which light emitted from an arbitrary point on the entrance surface 93 does not irradiate the entire area of the exit surface 94 as shown in FIG. , Rear or element lens exit surface 94 (FIG. 17)
The light beam intersects near the optical axis of the element lens,
Approximately connect the vertices (the focus is 1 because the light source is not a point light source)
Do not gather at the point).

When the element lenses are arranged as in the present invention, when a circular aperture stop is placed, all the element lenses are arranged almost at the center of the opening of the aperture stop. Therefore, if the position where the approximate focus of the element lens is brought close to the position where the ring-shaped aperture stop is arranged, most of the light emitted from the lens is not blocked, and the aperture of the ring-shaped aperture stop is not blocked. Part can pass through.

Incidentally, even in the case of the eighth embodiment, FIG.
FIG. 9A is similar to FIG. 9B, but FIG.
The same thing as the difference between FIG. Further, in the eighth embodiment, FIGS. 10A and 10B are similar, but this is the same as FIG. 5A and FIG.
There is a similar relationship to the difference in (b).

In the above-described first to eighth embodiments, light is prevented from transmitting through portions having no element lens.

(Embodiment 9) FIGS. 11 and 12 show ring-shaped element lenses 1 and 2 of Embodiments 1 to 5 shown in FIGS.
FIG. 10 is a cross-sectional view showing a state where other element lens groups 59 to 66 in which element lenses are regularly arranged vertically and horizontally like optical integrators of a conventional projection exposure apparatus are arranged inside 4, 10, 15 to 18. 11 and 12,
1a, 4a, 8a, 15a, 16a, 17a, 18a
Are the element lenses 1, 4, 8, 15, 16, 1
Element lens groups 59, 60, 61, 6 composed of 7, 18
Reference numerals 2, 63, 64, 65, and 66 denote element lens groups 1 respectively.
a, 4a, 8a, 15a, 16a, 17a, and 18a.

To perform projection exposure using a circular secondary light source, the larger the coherency factor σ is, the higher the resolution is, and theoretically, the maximum resolution is obtained when σ = 1. On the other hand, when performing projection exposure using a conventional circular secondary light source, it is considered that the coherency factor σ is most preferably a value from 0.4 to 0.6. Further, in order to use a phase inversion mask provided with a film for inverting the phase of light by 180 ° as an original substrate, it is necessary for the light to have a higher coherence.
Is used, a smaller value of about 0.2 to 0.4 is used.

[0096] In order to perform such wide applications at the same projection exposure apparatus, as shown in FIGS. 11 and 12, two types of element lenses using optical integrator from the group, the periphery of the element lens group 1a, 4a , 8a, 15a, 1
An aperture stop that allows only light from 6a, 17a, and 18a to pass and an aperture stop that allows light from some or all of the inner element lens groups 59 to 66 are prepared and selected. You can use it. Peripheral element lens group 1
a, 4a, 8a, 15a, 16a, 17a, and 18a, an aperture stop that allows only the light to reach the original substrate.
As shown in FIGS. 1 to 5 of the first to fifth embodiments, light from the entire area of the element lens groups 1a, 4a, 8a, 15a, 16a, 17a, and 18a may pass therethrough. As shown, a circular aperture stop may be used.

The aperture stop for allowing light from a part or all of the central element lens groups 59 to 66 to reach the original substrate has a circular shape or a shape similar to the contour of the element lens groups 59 to 66. For example, any shape may be used as long as illumination uniformity can be ensured. In some cases, light from element lenses in all regions of the element lens group as shown in FIGS. 11 and 12 may be used.

As described above, even when switching to which of the element lenses is used, the peripheral element lens groups 1a, 4a, 8a, 15a, 16a, 17a, 18a, which resemble a circle, are used.
In this case, the original substrate can be uniformly illuminated because both the light from the lens and the light from the central element lens groups 59 to 66 can uniformly irradiate the original substrate.

By the way, also in the ninth embodiment, FIG.
(A) and FIG. 11 (b) and FIG. 12 (a) and FIG.
(B) are similar to each other, but in this case, a gap formed between the outer ring-shaped element lenses and the centrally arranged element lens group at the center depends on the number of the element lenses. 11 (a) and 11 (b) and FIG. 12 (a) and FIG. 12 (b). The smaller the gap, the higher the efficiency of use of light rays, and the larger the aperture of the aperture stop that uses the central element lens group, the better the resolution and illumination uniformity. In terms of securing, the flexibility of the projection exposure apparatus increases, which is advantageous.

In addition, in the case of the ninth embodiment, when the exposure is performed by using the outer lens elements arranged in a ring shape, the distance between FIG. 1A and FIG. A relationship similar to the relationship between FIG. 2 and FIG.
There is a similar relationship between FIG. 5B and FIG. 5A and FIG. 5B of the fifth embodiment.

In the above embodiments, only the case where the element lenses are arranged in a shape similar to a circular ring has been described. However, in each embodiment, only a part of the element lens group arranged in a shape similar to a circular ring is described. It is evident that the same effect as that of obtaining a partial circular light source can be obtained by using the above or by arranging only a part from the beginning.

Further, similar to the embodiment shown in FIGS. 6 to 10 described above, a partial annular aperture stop may be used. In this case, a better result can be obtained by adjusting the position of the aperture of the aperture stop to a position where the element lens exists or a position including the center of the element lens.

As a special case, when the length of the arc of the partial ring is made substantially equal to the width of the ring, a rectangle or square having a size equal to the length of the arc or the width of the ring of the partial ring, or Prepare a rectangular or square element lens or element lens group slightly larger than the arc length or the ring width of the partial ring, or a circular element lens capable of enclosing one required partial ring. They may be arranged approximately concentrically, and a rectangular, square or circular aperture stop matching the element lenses arranged on the concentric circles may be used. An aperture stop as shown in Japanese Patent Application No. 59-212269, in which the light transmittance at the peripheral portion is larger than the light transmittance at the central portion, is used in a manner similar to the embodiment of FIGS. It goes without saying that it may be done.

In the above embodiment, an example is shown in which the element lenses of the optical integrator are arranged on a perfect circle. However, it is not always necessary to arrange them on a perfect circle. The radius of the circle does not have to be exactly the radius r of the required circular light source. A predetermined relationship needs to be established between the required radius r of the circular light source and the cross-sectional dimension of the element lens. However, if the element lens is arranged on a circle having a radius of about r, almost the same. The effect is obtained.

For example, in the first to fourth embodiments, the conditions for accurately arranging the element lenses having a rectangular or square cross section on a circle have been described. In the case where it is not possible to dispose the lens elements, it is possible to obtain substantially the same effect even if some element lenses are slightly shifted.

Also, FIGS. 6 (a) to 6 (d), FIGS.
As can be seen from (d), if the element lenses are arranged on an accurate circle and the circular aperture stop is arranged so that the center of the opening of the circular aperture stop is located at the circle, In some cases, the gap formed outside the circle and having no element lens is larger than the area of the gap formed without the element lens inside the circle. In this case, shifting the position of the opening of the circular aperture stop inward can reduce the light loss, and the position of the center radius of the opening of the circular aperture stop requires the radius r of the circular light source required. In this case, it is better that the radius of the circle where the element lenses are arranged is slightly larger than r. Similarly, in such a case, it goes without saying that some of the element lenses are not accurately arranged on the circle and may be slightly shifted.

As shown in Japanese Patent Application Nos. 59-212269 and 3-148133, the incident light is applied to the light incident side of the optical integrator, and a substantially circular ring is formed around the optical integrator. If the present invention is applied by improving the efficiency of use of light rays by devising to converge on a portion having the shape of, it is possible to improve the uniformity of illumination without lowering the intensity of light illuminating the original drawing substrate it can.

[0108] As in the embodiment shown in FIG. 11, 1 2, and a peripheral group of element lenses is similar to circular ring, an element lens in the center of the circular portion, the more and all of them, to a projection exposure when using selected to suit the shape of the fine patterns having the originals substrate, first shown in FIG. 13 to be effectively collected switched the light from the light source only in a portion of the element lens used in the optical integrator It is more useful to apply the present invention so that the illumination area of one illumination optical system 68 can be changed and the intensity of light illuminating the original drawing substrate is not reduced.

Further, in all the embodiments described above, element lenses having different shapes and cross-sectional dimensions may be appropriately combined and used. FIG. 4, FIG. 5 (d), FIG. 6 (d),
7 (d), 8 (d), 9 (d), 10 (d),
In FIG. 11D and FIG. 12D, in order to unify the dimensions of the element lenses corresponding to the width of the ring near the X axis and the Y axis,
Although element lenses with different cross-sectional dimensions were used,
In order to obtain a shape similar to a partial ring, element lenses having arbitrarily different shapes and cross-sectional dimensions may be used.

Further, in the above description, since there are many exposure targets usually having a rectangular or square exposure area like an LSI pattern, only the embodiment in which the cross section perpendicular to the axis of the element lens is rectangular or square is described. However, it is needless to say that the present invention is useful also in a case where an elemental lens having a cross section perpendicular to the axis such as a regular hexagon or a circle is preferable, such as when the entire region of a circular wafer is an exposure region.

[0111]

As described above, according to the present invention, in a projection exposure apparatus using a circular or partial circular secondary light source, the uniformity of illumination of the original substrate can be greatly improved. When transferring a fine pattern such as an LSI through an exposure optical system, there is an effect that the line width of the transferred fine pattern in the exposure region can be made uniform. Further, there is an effect that not only the uniformity of the illumination intensity of the original drawing substrate but also the incident angle distribution of the illumination light can be uniformed. Therefore, when a fine pattern such as an LSI is transferred through the projection exposure optical system, the resolution that can be transferred in the exposure area is made uniform, and the cross-sectional shape of the fine pattern can be made uniform.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical integrator showing one embodiment of the present invention.

FIG. 2 is a sectional view of an optical integrator according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an optical integrator according to a third embodiment of the present invention.

FIG. 4 is a sectional view of an optical integrator according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of an optical integrator according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of an optical integrator according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of an optical integrator according to a sixth embodiment of the present invention.

FIG. 8 is a sectional view of an optical integrator according to a seventh embodiment of the present invention.

FIG. 9 is a sectional view of an optical integrator according to an eighth embodiment of the present invention.

FIG. 10 is a sectional view of an optical integrator according to an eighth embodiment of the present invention.

FIG. 11 is a sectional view of an optical integrator according to a ninth embodiment of the present invention.

FIG. 12 is a sectional view of an optical integrator according to a ninth embodiment of the present invention.

FIG. 13 is a sectional view showing a basic configuration of an optical system of a conventional projection exposure apparatus.

FIG. 14 is a sectional view showing an optical system of a conventional projection exposure apparatus.

FIG. 15 is a cross-sectional view showing an optical integrator of a conventional projection exposure apparatus.

FIG. 16 is a correlation diagram showing a measurement example of an intensity distribution in an exposure area when a circular aperture stop is installed in an optical integrator of a conventional projection exposure apparatus.

FIG. 17 is a cross-sectional view showing how light travels in an element lens constituting the optical integrator.

FIG. 18 is a cross-sectional view showing how light travels in an element lens constituting the optical integrator.

FIG. 19 is a cross-sectional view illustrating a state in which an aperture stop is arranged on an element lens constituting the optical integrator.

[Explanation of symbols]

 1 element lens 2 circle 3 intersection

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G02B 26/02 G03B 27/32 G03F 7/20 521

Claims (2)

(57) [Claims] 1. A pattern on an original substrate is exposed through a projection exposure optical system using an aggregate of element lenses or an integrated element lens group as an optical integrator, and using light emitted from the optical integrator as a secondary light source. In a projection exposure apparatus for transferring light onto a substrate, light incident on the optical integrator may be a circular ring.
Or light collected in a partial ring shape, and the center of the element lens is approximately the radius of the ring.
Radius on the circumference of one circle or radius of the ring
A projection exposure apparatus comprising an optical integrator arranged so as to be arranged on an arc having a radius of . 2. An assembly of element lenses or an integrated lens
Use element lens group as optical integrator
The light emitted from the optical integrator is converted to a secondary light.
As a source, the pattern on the original
A projection exposure apparatus for transferring a pattern onto a substrate to be exposed, wherein the center of the element lens is approximately one circle.
Optical in line up or above the arc
A ring-shaped or partial-circular aperture stop having a tetegrator and an aperture stop having a ring shape or a partial ring shape provided on the emission side of the optical integrator so that the light transmittance of the peripheral portion is larger than the light transmittance of the central portion. Approximate circle of the center of the lens
The position of the circumference or the arc is the range of the aperture of the aperture stop of the ring or the partial ring, or the light transmittance of the peripheral portion.
The projection exposure apparatus is characterized in that the light transmittance at the periphery of the stop is larger than the light transmittance at the center .